Tankless with front load H/E washer? Not LG

Hello. I've been a member for a short time, reading up on tankless water heaters. I found Rinnai RC80HPi to be a perfect fit, and meets all specs to get every rebate and incentive possible. Except I asked a question about my LG H/E (front load) washer. At the start of each cycle, it "pulses" water into the drum. Its not often I hear a steady fill of water enter the washer.

So I emailed LG about this, and here's what they said:

"When using a tank less water heater, it is necessary to leave the water running before starting a wash cycle. If not the amount of water will not be enough to start the heating element and the unit will drag cold water in every cycle."

Well, thats not a surprising answer, but I was hoping for one that tells me how to actually make the washer work with a tankless heater. IMO, LG and may be other manufactures have goofed up. For a high efficient water heater not to work with a high efficient washer is a joke!

Well, thats not a surprising answer, but I was hoping for one that tells me how to actually make the washer work with a tankless heater. IMO, LG and may be other manufactures have goofed up. For a high efficient water heater not to work with a high efficient washer is a joke!

Any ideas?

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The heater is only a high efficient heater in some conditions, not all. For this to work you would need to run enough hot water to trigger the heater while you are doing the laundry, no other real way around it. The heater must read x gpm before it kicks on.

The heater is only a high efficient heater in some conditions, not all. For this to work you would need to run enough hot water to trigger the heater while you are doing the laundry, no other real way around it. The heater must read x gpm before it kicks on.

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I completely understand the problem...my post is more FYI and of surprise there is no work around other than running hot water elsewhere in orde for the washer to get hot water.

The problem is the washer cycling the water on/off every second or two as it fills the drum. In that time, there is enough flow to kick on the heater but not enough time to allow the the water heat! Thus the water will never be warm/hot going to the washer.

In my area, most new homes are getting tankless heaters and front loading washers, yet it seems no one has realized this issue? And that LG and others have not found a way to work with tankless water heaters? To me, that's shocking!

Have you thought about shutting off the hot water supply to the LG washer and only sending cold water to the unit? I believe the washer has an internal heater which would then heat the water internally to the required temperature. Would this approach solve the tankless water heater issue?

Have you reached any resolution on this issue? I am also interested in the Rinnai RC80HPi and currently have an LG front loading washer.

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Per LG, the washer does heat the water coming in but the rise in temp is in question. BUT, if it only gets cold water, the temp rise will not be enough to actually heat the water.

I would not install a tankless heater with these H/E washers without a recirculation pump or hybrid heater. Using a pump defeats the high efficiency of the heater and washer IMO, and I do not consider that realistic.

Since you already have the Rinnai only using a Hybrid is a moot question. Ran into this type of micro short on/off problem before with dishwashers and washers.
Bosch's solution is a 2.5 gallon Ariston Electric mini-tank at point of use. Works as this is a 115V heater and anytime you'd run out of hot water from it the tankless would be there with hot water to back you up. As flow brings hot water from tankless through the Ariston the t-stat shuts the Ariston down.
Basically you're making the tankless a hybrid at POU but with small electric rather than an internal reservoir as in the hybrids such as the Eternal GU195, GU145 and GU26 and GU32.
Most tankless now trigger at .5 GPM down from the old .75 GPM models of a few years back so this used to be even more of a problem. Therefore at a 2 GPM flow rate you'll get a little over a half gallon passage through the heater initiating and probably another .50-.75 GPM reaching temperature plus cooled water in pipping leading to appliance. I imagine if the LG is more efficient than my Frigidaire it uses 8 gallons or less per load. Don't most H/E Mfrs recommend using a Cold Water detergent ? Also isn't the fact they have a heater admission they know something isn't Kosher in their setup?
It's a non-perfect solution but about all you can do short of getting rid of that short cycle fill switch in the LG.
Tell me again Santa why a HE washer fills in spurts. It sounds somewhat moronic in the design.
FYI Been doing tankless for over 8 years sell, install and service Noritz. Bosch, Takagi/A.O. Smith, Rinnai, Eternal, Rheem going back to CEC 125VP and 38 so seen most every situation imaginable. I still believe in tankless but many times the wife says I'm a bit dingy.

The manual on my washer ( a Samsung) implies it adds water, then moves the drum to gauge if everything got wet and there is enough water to continue with the wash cycle. It does this a bit at a time, and would give a tankless grief, just like the LG, and probably most other front-loading WMs out there. I guess it does it that way to figure out if there's enough water to wash properly. It seems to do it by sensing how things slosh around and any imbalance (probably is using strain gauges). Mine also has a heater, but it is (only?) used if you select the sanitize cycle. Then, it superheats the water to kill anything that might be there, it is not generally used to just warm the water up (that I could figure out). It also adds considerably to the wash cycle duration. Many DW have a heater to bring the incoming water up to the required minimum for the detergents to work. It's a good idea to leave that on, as often, there can be a lot of cold water in the lines, and you end up filling part of it with cold, regardless of how it is connected. Plus, in most domestic situations, the max recommended output from a tank is 120-degrees, and DW like at least 130 to work their best. My tank is set to 140, but there's a tempering valve on the outlet to reduce it (per local codes) to 120.